The present invention relates to a technique for transmitting compressed moving picture data of a plurality of channels by using a serial transmission path of a single channel including a light, a radio wave and so on. The present invention is suitable for use in, for example, a video server system.
Conventionally, the waveform of an analog composite signal was examined by using an oscilloscope, and its rising time and frequency characteristics, for example, were measured. Then, it was determined whether desired characteristics were achieved. When this analog signal was subjected to transmission or the like, its waveform itself was thus handled so as to be able to reproduce a waveform close to the original one with as little degradation as possible.
By sampling and quantizing such an analog signal to convert it into a digital form, the signal could be handled simply as digits no matter whether the signal was recorded or transmitted. Therefore, occurrence of degradation was prevented by preventing mistakes in digits.
When in this case an electric signal was converted into a digital form and handled as digits (data), for example, sampled data of bits were often connected between two devices via a cable so as to make bits parallel and data were transmitted. Such a scheme was called a parallel interface or a parallel transmission. In an 8 bit system, eight different signals were sent simultaneously from a device on a sending side to a device on a receiving side at this time. For signals sent in parallel, a parallel clock to be used for shaping when transmitting data was sent on a ninth signal path together with the data. There was thus used such a configuration that the timing of reproducing data in the device on the receiving side was always kept correct and sent data could be reproduced without errors.
In such a parallel interface, data were grouped into a block (packet) form beforehand in order to send the data efficiently and a signal corresponding to block synchronizing was added to each block prior and then transmitted. In the scheme using the block synchronizing, a part of data required to be actually sent is first defined, and a reference signal specifying its position was inserted.
In the parallel interface, a parallel clock was transmitted between devices apart from the data as described above. On the other hand, in a serial interface, only data are transmitted successively by using one cable. In the serial interface, however, mutual conversion can be facilitated by utilizing conventions of the parallel interface to the utmost. As one satisfying such a condition, an SMPTE (Society of Motion Picture and Television Engineers) 259M was standardized. Such a serial interface prescribes a procedure for making data serial and sending the serial data and a procedure for making the data parallel again. In this way, it has become possible to conduct a long distance transmission over one cable which was impossible in the conventional parallel interface.
As against an SDI (Serial Digital Interface) scheme standardized in the SMPTE 259M, there was an SDDI (Serial Digital Data Interface) scheme individually developed by the applicant of the present invention. Though the SDDI scheme is suitable for multimedia and multichannel application, it has a high compatibility with the SDI scheme.
In a system hereafter described, picture data formatted in accordance with the SDI scheme is compressed and then converted into the format of the SDDI scheme, and compressed moving picture data of a single channel is transmitted over a transmission path of the SDDI scheme. First of all, the configuration of a transmitting device will now be described. In FIG. 1, the transmitting apparatus includes an SDI decoder 100 for restoring original digital data from moving picture data V formatted in the SDI scheme, a video bit rate reduction encoder 101 for compressing the digital data to approximately xe2x85x9, and an SDDI payload memory 102 for conducting preprocessing to convert the compressed moving picture data, audio data A formatted in the AES/EBU scheme and control data C to a format of the SDDI scheme at the time of writing.
Furthermore, the sending device includes an SDDI encoder 103 for adding a header portion and the like containing a synchronizing signal to payload data on the basis of a predetermined reference signal RF and generating data of the format of the SDDI scheme, and a serial interface transmitter 104 for serially transmitting the data of the format of the SDDI scheme as output data OD.
Here, the control data C is control data concerning the control of the moving picture data V and the audio data A. In the format of the SDDI scheme, the payload is a portion storing user data.
The transmitting apparatus having such a configuration conducts operation as hereafter described. When the moving picture data V formatted according to the SDI scheme is supplied to the SDI decoder 100, the moving picture data V is processed in the SDI decoder 100 so as to restore the original digital data represented by video data 113 in FIG. 3C. The restored original digital data is supplied to the video bit rate reduction encoder 101. In the video bit rate reduction encoder 101, the digital data is compressed in such a manner that four fields shown by the reference frame signal RF in FIG. 3A are compressed to approximately xe2x85x9. A resultant compressed state is shown in FIG. 3B. This compressed moving picture data, the audio data A denoted by 114 in FIG. 3C, and the control data C denoted by 112 in FIG. 3C are supplied to the SDDI payload memory 102. At the time of writing into the SDDI payload memory 102, the compressed moving picture data, the audio data A, and the control data C are stored for the payload in the state as shown in FIG. 3B.
The data stored for the payload is supplied to the SDDI encoder 103. In the SDDI encoder 103, the header portion and the like containing the synchronizing signal which is not illustrated are added to the payload data at every four fields on the basis of the reference frame signal RF shown in FIG. 3A, so that data 110 having the format of the SDDI scheme is generated as shown in FIG. 3B. The data 110 of the format of the SDDI scheme is supplied to the serial interface transmitter 104. In the serial interface transmitter 104, the output data OD having the format of the SDDI scheme as shown in FIG. 3B is serially transmitted as the data 110 at every four fields represented by the reference frame signal RF in FIG. 3A. In the same way, data is generated in the next four fields.
The configuration of a receiving apparatus will now be described. As shown in FIG. 2, the receiving device includes a serial interface receiver 105 for receiving the output data OD having the format of the SDDI scheme as shown in FIG. 3B, an SDDI decoder 106 for restoring the original digital data from the output data OD having the format of the SDDI scheme, and an SDDI payload memory 107 for storing the restored original digital data and dividing the restored original digital data into the compressed moving picture data, the audio data A, and the control data C at the time of reading.
Furthermore, the receiving apparatus includes a video bit rate reduction decoder 108 for conducting expansion processing on the compressed moving picture data, and an SDI encoder 109 for converting the moving picture data subjected to the expansion processing to the format of the SDI scheme and outputting the original moving picture data V.
The receiving apparatus having such a configuration conducts operation heretofore described. The output data OD of the format of the SDDI scheme is supplied to the serial interface receiver 105. In the serial interface receiver 105, the output data OD of the format of the SDDI scheme is received. The received output data OD of the format of the SDDI scheme is supplied to the SDDI decoder 106. In the SDDI decoder 106, the original digital data is restored from the output data OD of the format of the SDDI scheme. The restored original digital data is supplied to the SDDI payload memory 107. In the SDDI payload memory 107, the original digital data is stored. At the time of reading, the original digital is divided to the compressed moving picture data, the audio data A, and the control data C.
The compressed moving picture data obtained by the division is supplied to the video bit rate reduction decoder 108. In the video bit rate reduction decoder 108, the compressed moving picture data is subjected to the expansion processing. The original moving picture data subjected to the expansion processing is supplied to the SDI encoder 109. In the SDI encoder 109, the moving picture data is converted to the format of the SDI scheme and output as the original moving picture data V. The audio data A and the control data C obtained by the division are output as they are.
In this way, it is possible to convert the moving picture data A of a single channel of the SDI scheme to the compressed moving picture data and transmit the compressed moving picture data together with the audio data A and the control data C as the output data OD of the format of the SDDI scheme via the SDDI transmission path.
In the case where a compressed moving picture transmission system of two or more channels is formed by using such a single-channel compressed moving picture transmission system using a conventional SDDI transmission path, however, it is indispensable in the device of the sending side to provide a function of disposing data of channels in an arbitrary place of a data area of the SDDI format so that they may not overlap each other in order to be able to flexibly cope with a change in the number of respective channels to be transmitted and a change in data size of respective channels. Furthermore, it is indispensable in the receiving apparatus to provide a function of correctly extracting data of respective channels disposed in the arbitrary place of the data area of the SDDI format.
Furthermore, for implementing such a function in the sending device and the receiving device, in the sending device, for example, the operation for writing data to be sent onto the SDDI format into the internal SDDI payload memory beforehand and making preparation becomes complicated. This results in a disadvantage that the circuit configuration differs largely from that of the sending device of compressed moving picture transmission of a single channel and becomes a large scale.
When it is attempted to implement compressed moving picture transmission limited to two channels by using such a single-channel compressed moving picture transmission system using a conventional SDDI transmission path, therefore, the device has a configuration largely exceeding the scale of two single-channel compressed moving picture transmission systems. In addition, there occurs a disadvantage that the configuration of the single-channel compressed moving picture transmission system cannot be diverted as it is.
The present invention has been made in view of such problems. An object of the present invention is to provide a sending device, a receiving device, and a sending/receiving device capable of implementing a two-channel compressed moving picture transmission system by using the existing single-channel compressed moving picture transmission system with ease.
The sending device of the present invention is a sending device including a plurality of sending systems, each of the sending systems including compression means for compressing picture data, and serial signal generation means for adding a predetermined synchronizing signal to compressed picture data compressed by the compression means and thereby generating predetermined serial signal data, serial signal data of a plurality of channels being sent from the plurality of sending systems, in which there is provided a changeover means for changing over between the serial signal data of a certain channel output from the serial signal generation means of the sending systems and serial signal data of another channel output from the serial signal generation means of another sending system included in the plurality of sending systems, according to a changeover signal based upon the synchronizing signal, and the serial signal data of the certain channel and the serial signal data of the another channel are serially transmitted according to the changeover signal.
A receiving device of the present invention is a receiving device including a plurality of receiving systems, each of the receiving systems including serial signal detection means for detecting compressed picture data and a predetermined synchronizing signal from serial signal data obtained by adding the predetermined synchronizing signal to the compressed picture data, and expansion means for expanding the compressed picture data detected by the serial signal detection means and thereby restoring original picture data, serial signal data of a plurality of channels being received and the original picture data of the plurality of channels being output from the plurality of receiving systems, in which there is provided a changeover means for outputting the compressed picture data output from the serial signal detection means to the receiving system of a certain channel and another receiving system of another channel included in the plurality of receiving systems changed over according to a changeover signal based upon the synchronizing signal, and changeover between the compressed picture data of the certain channel and the compressed picture data of the another receiving system is conducted according to the changeover signal, and thereby original picture data of the certain channel and original picture data of the another channel are output from the receiving system and the another receiving system.
A sending/receiving device of the present invention is a sending/receiving device including a sending unit and a receiving unit, the sending unit including a plurality of sending systems, each of the sending systems including compression means for compressing picture data, and serial signal generation means for adding a predetermined synchronizing signal to compressed picture data compressed by the compression means and thereby generating predetermined serial signal data, serial signal data of a plurality of channels being sent from the plurality of sending systems, the receiving unit including a plurality of receiving systems, each of the receiving systems including serial signal detection means for detecting the compressed picture data and the synchronizing signal from the serial signal data, and expansion means for expanding the compressed picture data detected by the serial signal detection means and thereby restoring original picture data, serial signal data of a plurality of channels being received and the original picture data of the plurality of channels being output from the plurality of receiving systems, in which in the sending unit, there is provided a changeover means for changing over between the serial signal data of a certain channel output from the serial signal generation means of the sending systems and serial signal data of another channel output from the serial signal generation means of another sending system included in the plurality of sending systems, according to a changeover signal based upon the synchronizing signal, and the serial signal data of the certain channel and the serial signal data of the another channel are serially transmitted according to the changeover signal, and in the receiving unit, there is provided a changeover means for outputting the compressed picture data output from the serial signal detection means to the receiving system of a certain channel and another receiving system of another channel included in the plurality of receiving systems changed over according to a changeover signal based upon the synchronizing signal, and changeover between the compressed picture data of the certain channel and the compressed picture data of the another channel is conducted according to the changeover signal, and thereby original picture data of the certain channel and original picture data of the another channel are output from the receiving system and the another receiving system.
Furthermore, a transmission device of the present invention is a transmission device for transmitting video data of a plurality of channels, in which there are provided compression means for compressing video data of a first channel and video data of a second channel and thereby generating first compressed video data and second compressed video data, conversion means for converting the first compressed video data and the second compressed video data to a predetermined serial transmission format, and transmission control means for controlling transmission timing of the first converted compressed video data and the second converted compressed video data such that the first compressed video data and the second compressed video data converted to the predetermined transmission format by the conversion means are transmitted by using one serial transmission system.
Furthermore, a transmission device of the present invention is a transmission device for transmitting video data of a plurality of channels, there are provided compression means for compressing video data of a first channel and video data of a second channel each having a predetermined interval length and thereby generating first compressed video data and second compressed video data, and transmission means for multiplexing and transmitting the first compressed video data and the second compressed video data such that the first compressed video data and the second compressed video data are transmitted in the predetermined interval by using one serial transmission system.
Furthermore, a transmission method of the present invention is a transmission method for transmitting video data of a plurality of channels, in which video data of a first channel and video data of a second channel are compressed thereby generating first compressed video data and second compressed video data, the first compressed video data and the second compressed video data are converted to a predetermined serial transmission format, and transmission timing of the first converted compressed video data and the second converted compressed video data is controlled such that the first converted compressed video data and the second compressed video data and the second converted compressed video converted to the predetermined format are transmitted by using one serial transmission system.
Furthermore, a transmission method of the present invention is a transmission method for transmitting video data of a plurality of channels, in which video data of a first channel and video data of a second channel each having a predetermined interval length are compressed thereby generating first compressed video data and second compressed video data, and the first compressed video data and the second compressed video data are multiplexed and transmitted the first compressed video data and the second compressed video data are transmitted within the predetermined interval by using one serial transmission system.
The transmitting apparatus of the present invention operates as heretofore described.
In the first channel transmitting system, picture data of the first channel is supplied to the compression means. In the compression means, picture data corresponding to four fields is compressed to approximately xe2x85x9. This compressed picture data is supplied to the serial signal generation means. In the serial signal generation means, a header part and the like including the synchronizing signal are added to the compressed picture data of the first channel in the field 1 at every four fields on the basis of the changeover signal and thereby serial signal data of the first channel is generated.
Furthermore, in the second channel sending system, picture data of the second channel is supplied to the compression means. In the compression means, picture data corresponding to four fields is compressed to approximately xe2x85x9. This compressed picture data is supplied to the serial signal generation means. In the serial signal generation means, a header part and the like including the synchronizing signal are added to the compressed picture data of the second channel in the field 2 at every four fields on the basis of the changeover signal and thereby serial signal data of the second channel is generated.
Furthermore, the serial signal data of the first channel generated in the serial signal generation means of the first channel is supplied to one of the stationary contacts of the changeover means. The serial signal data of the second channel generated in the serial signal generation means of the second channel is supplied to the other of the stationary contacts of the changeover means. Here, the changeover means is supplied with the changeover signal, so that on the basis of the changeover signal, the movable contact of the changeover means is selectively connected to one or the other of the stationary contacts according to the distinction of the field 1 or the field 2 at every four fields.
In association with the field 1 or the field 2 at every four fields, therefore, the serial signal data of the first channel or the serial signal data of the second channel is selectively output from the movable contact of the changeover means at changed timing.
The serial signal data of the first channel or the serial signal data of the second channel thus output selectively at changed timing by the changeover means and the changeover signal so as to correspond to the field 1 or the field 2 at every four fields is serially transmitted as the serial signal data of the first channel or the serial signal data of the second channel at every four fields indicated by the changeover signal.
The receiving device of the present invention operates as heretofore described.
The serial signal data is supplied to the serial signal detection means. The serial signal detection means is supplied with the changeover signal, so that in the serial signal detection means, the original compressed picture data of the first channel and the second channel are restored from the serial signal data so as to correspond to the interval of the field 1 or field 2 at every four fields of the changeover signal.
In other words, the serial signal detection means detects the clock from the data string, detects the synchronizing signal such as the synchronizing word or the like and data, conducts channel decoding for data transmission, and restores scrambled data to their original arrangement. It is prescribed that the restored data string should be sent in the order beginning with the LSB and ending with the MSB. Therefore, operation of attaining synchronization and determining where on the data the LSB is located is conducted.
In this case, the clock is detected by taking a change point of the data string as the reference. When the synchronizing word has been detected, an immediately succeeding bit is judged to be the LSB. By taking the LSB as the reference, word synchronizing is attained. Once this word synchronizing is detected, bits are counted thereafter.
The original compressed picture data of the first channel and the second channel restored are supplied to one movable contact of the changeover means. The control terminal of the changeover means is supplied with the changeover signal. On the basis of the changeover signal, therefore, the other movable contact of the changeover means is selectively connected to one stationary contact or the other stationary contact according to the distinction of the field 1 or the field 2 at every four fields.
In association with the field 1 or the field 2 at every four fields, therefore, the original compressed picture data of the first channel or the original compressed picture data of the second channel is selectively output from one stationary contact or the other stationary contact of the changeover means at changed timing.
In the receiving system of the first channel, the original compressed picture data of the first channel is supplied to the expansion means. In the expansion means, the compressed moving picture data is subjected to expansion processing. The original moving picture data subjected to the expansion processing is output as the moving picture data of the first channel.
In the receiving system of the second channel, the original compressed picture data of the second channel is supplied to the expansion means. In the expansion means, the compressed moving picture data is subjected to expansion processing. The original moving picture data subjected to the expansion processing is output as the moving picture data of the second channel.
In this way, the conventional single-channel compressed moving picture transmission system is diverted to arrange compressed moving picture data of two channels at timing of the interval of the field 1 or the field 2 at every four fields, whereby the compressed moving picture data of the two channels can be serially transmitted by using one coaxial cable.
The sending/receiving device, the transmission device, and the transmission method of the present invention operates as heretofore described.
Picture data of the first channel is supplied to the transmitting system of the transmitting unit for the first channel. Picture data of the second channel is supplied to the sending system of the sending unit for the second channel. In the sending system for the first channel and the sending system for the second channel, the picture data of the first channel and the picture data of the second channel are subjected to compression processing. The moving picture data of the first channel and the moving picture data of the second channel subjected to the compression processing are converted to serial signal data at changed timing so as to be serially arranged and serially transmitted via one coaxial cable.
Upon receiving in the receiving unit the serial signal data transmitted from the sending unit, the serially arranged data are separated into the first channel and the second channel. The picture data of the first channel and the picture data of the second channel subjected to the compression processing in the first channel sending system and the second channel sending system of the sending unit are subjected to expansion processing. The picture data of the first channel and the picture data of the second channel subjected to the expansion processing are output as the original picture data of the first channel and the original picture data of the second channel.